Mercury switch



9 H. E. BU.CKLEN 2,091,803

- MERCURY SWITCH Filed May 19, 1932 Jvwhfw? Patented Aug..3 1, 1937 nmaouay swrrcn Herbert E.. Bucklen, Elkhart, Ind, assignmo! one-fourth to Paul 8. Bear, Dowagiac, Mich.

Application May 19, 1932, Serial No. 612,217

11 Claims. (Cl. 200-152) The present invention relates to electric switches in general and more particularly to switches of the type wherein the circuit is interrupted by the movement of a body of mercury.

Mercury switches generally comprise asmallbulb or capsule into which extend a pair of spaced electrodes that are bridged by a body of mercury when the switch is in a certain position, the arrangement being such that the mercury flows from its circuit closing position as the switch is turned or rotatedf Switches of this type are frequently arranged to be operated by a slow moving member, such as a thermostat, a clock mechanism, or the like. As the switch is rotated or tilted by its actuator the body of mercury slowly moves towards its circuit interrupting position. The movement of the mercury is very slow and when the first gap is produced in the circuit its length is being increased very slowly by the slow movement of the switch under control ofits actuator. the gap, said spark or are being interrupted only when the gap has reached such a size as to prevent voltage flash-over. This is an objectionable condition and it is one of the objects of the present invention to provide a mercury switch wherein the circuit is interrupted by a snap movement of the mercury eventhough the switch itself is being actuated very slowly as by a thermostat or the like. I accomplish this result by providing an arrangement that utilizes the surface tension of the mercury to retain the same against producing the initial gapin the circuit until such time as the switch has been moved to such a position that the gravitational force on the mercury is sufiicient to overcome the surface tension and immediately move the mercury its full amount regardless of further movement of the switch itself.

A further object of the invention is to employ" the surface tension of a part of the mercury conductor for moving another part of the mercury after the travel of the mercury has been initiated.

It is a further object of the present invention to provide a mercury switch wherein the circuit is interrupted by producing a series of gaps in a body of mercury whereby the voltage across any one gap is small. This not only reduces the amount of heat generated with each circuit interruption but it also distributes the generated heat therebyavoiding localized hot spots. Such an arrangement isparticularly useful where the switch is used to' flre'duently interrupt a circuit, a

in the case or flasher'sor' the like.

As a result a spark or arc forms across Another object of the present -invention is to provide a mercury break switch in which the point of contact making and contact breaking is sharply defined, whereby contact is made and broken repeatedly at a single point in the tilting movement of the switch, so that accurate "repeat performance is provided, that is, the circuit is'repeatedly broken at a predetermined point and in exactly the same manner is repeatedly made at the same predetermined point. This action is further intensified by the provision of a knife edge over which the mercury is attenuated just prior to breaking of the contact. By the attenuation of the mercury, and also by reason of the novel construction of the switch, the edges of the mercury at the instant of breaking or makingcontact are moving in opposed straight line directions,

whereby the snap action of the switch is practically doubled in speed due to the simultaneous opposed movement of these edges. Further, by the provision of this type of movement, direct "head-on collision or impact of the two edges of mercury, each moving at high speed, occurs, whereby contact is made with substantially no frying or sputtering between the meeting edges,

as the inertia of movement is too great to allow such action, which action also is induced somewhat by magnetic choking of these two edges.

Another-advantage of the present invention is the provision of one or more relatively large reservoirs or pockets into which the mercury moves as the circuit is broken, and which are capable of allowing continuing movement of the mercury during and after breaking of the circuit, whereby tion with the accompanying drawingsforming a part thereof. e

y In the drawings:

Figure 1 is aside view ofa switch embodying the principles of my invention;

Figure 2 is a sectional view taken along the lin 2-2 of Figure l and showing the switch in its closed position;

Flgure3isaviewsimilartpFigure2an showing the switch in its open position;

Figure 4 is a plan view of the switch shown in Figure 1, said view showing the position of the glass or the like within which the various parts are mounted and which is thereafter exhausted of its air and optionally filled with an inert gas, and sealed, as in the usual practice. The bottom of the tube is projected upwardly to define two flat surfaces 3 and 4 meeting at a ridge 5. The

ridge 5 extends longitudinally of the tube from end to end and constitutes a line of demarcation between a-mercury receiving pocket 1 and one or more pockets 8. when the switch is in its 2o closed position a body of mercury 9 within the switch will be entirely within the pocket I whereas' when the switch is in its open position the body of mercury will be in the pocket 8. Electrodes II and 12 extend into the glass tube 1 from the opposite ends thereof, both of the electrodes extending into the pocket 1 and being bridged by the body of mercury when the mercury is in the pocket I.

A plurality of glass separators I5I5 are secured within the tube 1, said separators being sealed to the wall of the tube and to the bottom of the portion 3 and to the part of the portion 4. Each separator has a blunt substantially knifelike edge ii directed towards the pool of mercury 9 in the pocket I, said blunt edge being defined by flarly disposed front walls III|. The walls lI- -II are at a rather large angle to one another whereas the rearwardly extending walls I8I 8 make a more acute angle with one another. The

degree of angularity may vary and the sides and edges may be rounded if desired, -as the purpose of these separators is first to provide lines of breakage of the continuity of the mercury conductor, and, second, to define between these Venturi tubes. It is to be noted that adjacent glass separators are spaced apart to provide openings' through which the mercury may spill from the pocket I into the pocket 8. The openings are wide at the front and have restricted throats be- 5 tween the edges 202l of adjacent separators and thereafter again become wide. It is thus apparent that the openings comprise- Venturi openings through which the mercury can flow from the pocket I to the'pocket 8.

The circuit through the switch is controlled by rotating the switch tube I axially whereby the mercury spills from the pocket 1 into the pocket 8 and vice versa. Assume that the switch is being rotated colmterclockwise from the position 0 shown in Figure 2 in order to open the switch.

7 As the switch is rotated the surface I approaches a horizontal position and tends to cause the mer- However, the

edge of the pool of mercury. is brought into abut-' ment with theglas separators I5-l5 and therecury to spill into the pockets 8.

fore the mercury cannot spill into the pockets I without first permitting theseparators to overc0methe surface tension of the mercury. As the oif the switch continues there is an increase ofthe gravitational force tending to cause the mercury to spill over the ridge 5 into the pockets 8. Praently this force becomes equal to -theforoeofthesurfacetenslontendingtoresist the movement into the pocket, 8. The slightj5est additional movement of the tube I causes the 'mercury from running down the incline.

mercury to break into a series of pools each of which passes between two adjacent glass separators l5. Figure 4 shows, in diagrammatic form, the shape of the body of mercury immediately before it spills into the pocket 8. It is to be noted that at this time a portion 25 of the mercury is already over the longitudinal ridge 5 but is held from breaking away from the rest of the mercury by the surface tension between it and the portion of the mercury that is still on the part I of the tube I. The inclination of the floor wall to the horizontal is so low that during the initial stage of switching; the surface tension will have an appreciable cfiect in keeping the In other words, the tendency of the mercury to run down the incline is overcome by the cohesion and surface tension of the remainder of the body of mercury, so that atension between two parts of the body of mercury is produced. After the surface tension and cohesion are once broken, the mercury which tends to run down the incline will be free to do so. A slight additional tilting of the tube I causes adjacent pools of mercury to break apart at the edges I6 of the glass sepa rators. As the mercury moves into the position shown In Figure 4, it will be noted that the leading portions 25 of the mercury in the pockets 8 are still spaced considerably away from the rear walls of the pockets. The connecting portions of mercury engaging walls H and knife-edge [6 are, at this time, being attenuated under tension stresses imparted thereto by the cohering characteristlcs of the mercury, and. are being stretched over the edge 16 in the same mannor that a rubber band may be stretched over a knife edge. This attenuation of the mercury increases as the main body of mercury piles upin the dam-like restriction between the walls 20. At the movement of break, the pull of the main body of mercury overcomes the limits of cohesion of the mercury across the edge l6, and

the two continuous edges recede in opposite directions away fromtheedge, thus opening a gap at double the velocity of recession ofv one of the edges. At the same time, the main body of mercury 25 moves down into the pockets 8 through the diverging Venturi-like spillway, and by reason of the fact that the volume of mercury in each pocket is considerably less than the volume of the pocket the mercury continues to move rapidly toward the rear wall of the pocket. This ability to move further rearwardly of the pocket after the break is of importance in providlng'for snap-action opening of the circuit. Once this break occurs the separate pools of mercury will immediately flow into the pocket I since the surface tension of the body of mercury 25 already in the pocket 8 will pull the remainder of the mercury with it. This produces a quick lengthening of the gap between adjacent bodles oi mercury quite independent of the rate of the additional rotation of the tube. It is to be noted that as the body of mercury moves into the pocket I there are formed a plurality of gaps in the circuit, one gap being formed at each of the edges l6 of the glass separators as the mercury breaks into its various globules. Since the tube I is mounted in a horizontal position and the various parts are symmetrically located it follows that all of the gaps will b'e-produced at the same time, resulting in a very speedy interruption of the circuit once the interruption commences, and also resulting in a distribution of the heat generated. The

Venturi tubes produce a beneficial action, which is comparable to the snap action in a mechanical switch. The mercury has great surface tension and it does not tendto wet the glass 5 walls. Hence, it tends to assume at all times a globular form. This formis modified by the weight or gravity pull, and although the globule tends to flatten down, it still tends to retain very definitely a cohesive circular figure. Therefore the mercury as it tends to enter the restricted part of the Venturi tube resists distortion out of circular form. Hence, a slightly greater tilt of the tube is required to force the mercury to flow through the restricted area. But after the mercury once begins to flow through the restriction, it will continue the motion without further tilt of the container. This motion is ac celerated by the mass of mercury which has proceeded past the restricted or throat portion 7 0 of the venturi. The mass beyond the throat is greater than the mass in front of the throat, and hence the tendency of the larger mass to assume the spherical formoverpowers the like tendency of the smaller mass and tends to move both masses even though there be no further inclination of the tube. Hence the effect is to present initial resistance to travel of the mercury through the throat, but after the travel is once initiated, it proceeds to a break with an 0 accelerated motion without.v further inclination of the tube. v

The draft effect of the Venturi tube may be varied by the rate oftaper'of the parts of the Venturi tube and the mass of the body of iner- 5 cury employed- I wish to point out that the structure which I have herein disclosedfhas a novel mode of operation which is greatly superior to the mode of operation of known structures wherein a hori- 40 zontally extending barrier or dam is interposed in the pathpf the mercury travel. In those constructions, 'when the body'of mercury rises back of the dam or restriction, the top part of the body of mercuryv carrying the floating impurities spills over, carrying such impurities against.

the contacts to make the initial contact; 1

Also, it will be observed that the thin: spilling portion does not provide a large cross section of conducting material and, hence, if heavy current is flowing, tends to heat and vaporize.

By my construction, the convex vertically extending opposed surfaces define a passageway which is laterally constricted, asa stream is constricted by wing dams. Thesurface tension of the mercury at its advancing edge tends to keep the mercury from flowing through the constriction. As'the envelope is further tilted, the depth of mercury at the throat of the dams is increased and the hydraulic head of the mercury 6 is increased. This increase is, of course, greatlast to go through the restriction. This action- 70 is again? exhibited in the opposite direction when the mercury flows 'back through the restriction to make the return flow.

In making contact the reverse action occurs,

and the leading edges of the mercury spread out 75 after passing through the restriction and simultaneously move toward each other along the surfaces ll. Since each of the edges is moving. at a rapid rate toward the edge It, the rate at which the gap is closed is doubled and a substantial head on collision of the two contiguous 5 edges occurs, the inertia of movement of the two edges, by reason of the large volume of mercury pushing them forward, serving to produce an impactwhich breaks up the convexity of the abutting surfaces, and together .with the cohering 10 tendency of the mercury and the rate of movement thereof, cause uniting of the adjacent portions of mercury with substantially no frying or sputtering, thus providing a-snap action circuit I closing movement. 15

This switch has a very high degree of what may be termed repeat performance, that is, by reason of edge I6 the-contact will be made and broken repeatedly at the same point of tiltber or complete. Venturi' tube as distinguished 30 :from the open topped Ventu'ri tube or channel shown in Figures 1 to 4. Slots 3l are provided in the ceiling member 30 to permit-the flow of mercury from the chamber 8' upon the continued rotation of the tube l in a counterclockwise direc- 35 tion and also to permit the flow of gases from M the chamber 8 in the event that the tube is filled with inert gas or gases. In theforrn shown in Figures 1 to 4, the ridge 5 is located a short distance back of the minimum space or throat be- 40 tween adjacent partitions I5.- -l5. This varies slightly the location of the maximum restriction or throat and for a given amount of mercury controls the minimum thickness of the mercury in front of the points or noses it. In other re- 45 spects this switch is the same as that previous described.

Reference is herein made to a free surface of the mercury. By this'it is intended to refer to the surface of the mercury which is'not in engagement with a confining or supporting wall. Reference is also made to a free edge of the. mercury. This term is employed to designate the edge of the body of mercury where it is not confined by the containing walls, but is dependent upon its own cohesion or surface tension. Thus a body of mercury upon a flat horizontal plate wcuidhave a free edge completely around it.

It is an important concept of the present in-- vention that one-part of the body of mercury is .00 restrained from movement while another part travels with a free edge, and may thereby acquire inertia of motion. Then the portion which has thus acquired inertia of motion pulls the body of mercury apart at a definite predeter- 65 mined point, as, for example, on the edges lB-IG, where the body is to be parted, and the surface tension and cohesion whips the severed ends away from each other. This gives a sharp snap action or breaking at a definite point or position, which may be duplicated as often as desired.

' In compliance wit the requirements of the patent statutes I have erein shown and described a few preferred embodiments of my invention. It is however to be understood that the invention is not limited to the precise constructions herein shown, the same being merely illustrative. What I consider new and desire to secure by Letters Patent is:

. 1. A mercury switch comprising a horizontally mounted tube having a plurality of separators mounted therein, adjacent separators defining Venturi openings.

2. A mercury switch comprising a horizontally mounted tube having a plurality of separators mounted therein, adjacent separators defining Venturi openings, each separator having a blunt edge for piercing the surface film of a movi body of mercury. 1

3. In a mercury switch, an envelope, a pair of contacts extending into said envelope, a body of mercury for connectingsaid contacts, and a substantially vertical vane disposed in said envelope and disposed between said contacts, said vane having a relatively thick forward portion and a relatively thin rear portion to define Venturi-like channels on each side of the vane.

4. In a switch of the class described, an envelope, a pair of leads, a body of conducting liquid, and a substantially vertical double tapered vane thickest intermediate its ends and disposed be-' tween the leads for separating the conducting liquid by angular motion of the envelope.

5. In a switch of the class described, an envelope, leads extending through the walls of the envelope, a body of conducting fluid for connecting said leads, and a plurality of Venturi-shaped passageways arranged side by side within said envelope through which passageways portionsof the conducting fluid are caused to flow to break the connection between said leads at a plurality of points in series.

6. In a switch of the class described, an envelope, leads extending through the walls of the envelope, a body of conducting fluid for connecting said leads, and a Venturi-shaped passageway through which a portion of the conducting fluid is caused to flow to break the connection between said leads, said passageway having an inclined top wall, the lowest portion of which is adjacent the constricted portion of said passageway.

l. A mercury switch comprising a tube, circuit terminals extending into the tube, a body of met cury in said tube for connecting and disconnecting said terminals, and means within the tube defining separate parallel channels disposed transversely of a line drawn between the terminals for the flow of said mercury into separate parts, said channels having restricted central portions to provide Venturi-like passageways extending transversely of said tube, said means providing multiple breaks of the circuit in series.

8. In a mercury switch, an envelope provided with a pair of circuit terminals having contact portions within said envelope, 9. body of conducting liquid in said envelope, and a vane transversely disposed between said terminals, said vane comprising a convergent forward portion to divide the fluid, a thick portion adjacent said forward portion and a thinner rear portion to permit widening of the stream of liquid flowing on each side of the vane after said liquid passes the thick central portion of the vane.

9. In a mercury switch, the combination of a housing provided with a pair of terminals insulated from each other, a body of mercury in the housing adapted to contact with said terminals, and an insulating barrier adapted to part the mercury upon predetermined motion of the housing, said barrier having a thick forward portion and a narrower back portion to assist in accelerating the travel of the mercury to secure the parting action.

10. In a mercury switch, an envelope, a pair of contacts therein, a plurality of vertical projections defining channel-shaped Venturi passageways extending normal to a line drawn between said contacts, a body of mercury in said envelope and movable through said passageways in opposite directions upon tilting of said envelope, said projections providing knife-like edges for shearing said mercury into separate bodies to pass through said several passageways, the projections being formed to cause the trailing edges of mercury leaving said contacts and knife-like edges to snap toward each other in a direction normal to the direction of movement of the main body of mercury through the passageway whereby the rate of separation of contact is substantially twice the normal rate of movement of the main body of mercury.

ll. In a mercury switch, an envelope, 2. pair of contacts therein, a plurality of vertical projections defining channel-shaped Venturi passageways extending normal to a line drawn between said contacts, a body of mercury in said envelope and movable through said passageways in opposite.

directions upon tilting of said envelope, said projections causing the advancing edges of said bodies of mercury moving through said passageways upon bridging of contact to approach the contacts and each other in a direction normal to the direction of movement of the main portions of mercury, whereby substantially head-on contact-making collision of said edges occurs at substantially twice the rate of movement of said main portions of mercury.

HERBERT a. BUCKLEN. 

